The fact that you say calories in == calories out is typical of my complaint. Follow the metabolic pathway of glucose versus fructose in the liver and you quickly see a calorie is not a calorie, and many types of calories are much worse for you than others. Look at how ketones impact cell efficacy (admittedly, early results in rats hearts) and contrast that with conventional wisdom of "ketones are poison" and you can see the study of nutrition and obesity has not followed the study of biochemistry and endocrinology at all.